The present invention relates to a semiconductor integrated circuit device and a technique of fabricating a semiconductor integrated circuit device, and more particularly to measures for preventing corrosion of an upper-layer wiring when a TiN film is formed inside a through-hole for connecting upper- and lower-layer wiring formed over a semiconductor substrate and over an upper electrode of a capacitor insulating film, by a chemical vapor deposition method using a metal source containing a halogen element.
When the aspect ratio of a through-hole (depth/diameter of the through-hole) for connecting upper- and lower-layer wirings formed on a semiconductor substrate is increased as an LSI is further refined and more densely integrated, it is difficult to deposit a conductive film for wiring in the through-hole. Therefore, an art for embedding a plug in a through-hole having a high aspect ratio in a plug has been used so far.
As described in Japanese Patent Laid-Open No. 204144/1996, to prevent reaction between a metal wiring layer in a microminiaturized contact hole and an underlying layer, a titanium nitride (TiN) film is used as a reaction barrier layer.
The titanium nitride film, when deposited by a CVD (Chemical Vapor Deposition) method, has a good coverage and is thus widely used as a plug material buried in a through-hole with a high aspect ratio. For example, Japanese Patent Laid-Open No. 45770/1997 discloses a technique whereby a TiN film is formed by a CVD method inside a through-hole formed in an interlayer insulating film and a tungsten film or a tungsten compound is formed over the TiN film.
A technique has been developed which deposits a TiN film as an upper electrode by a CVD method over a tantalum oxide film which is a capacitive insulating film of a capacitor. For example, Japanese Patent Laid-Open No. 219501/1997 discloses a technique for forming a TiN film as an upper electrode over a tantalum oxide film as a capacitor insulating film by a CVD method.
To deposit a TiN film by the CVD method, a source gas containing a halogen element such as titanium tetrachloride (TiCl.sub.4) is generally used. This is because a TiN film formed by using the source gas has a large step coverage and moreover, the film can be formed at a low temperature of approx. 450.degree. C. and thereby, there is an advantage that the characteristic of a device is not deteriorated.
However, because a TiN film formed by using a source gas containing a halogen element contains a halogen element such as chlorine produced due to decomposition of the source gas, there is a problem that the Al (aluminum) wiring formed on a through-hole in which a CVD-TiN film is embedded would be corroded because the halogen element reacts with Al. In a method of forming a tungsten film or tungsten compound film over a titanium nitride film buried in a through-hole, as described in Japanese Patent Laid-Open No. 45770/1997, although the tungsten film has a greater capability to trap halogen elements than a tungsten compound film such as a tungsten nitride film, the overall effect of trapping halogen elements by the tungsten film is small, allowing halogen elements to enter the aluminum wiring layer formed over the tungsten film, and resulting in the halogen elements corroding the aluminum. Further, the tungsten film has a poor adhesion to the underlying film and is easily peeled.
An object of the present invention is to provide a method of preventing corrosion of an Al wiring formed over a through-hole in which a CVD-TiN film is buried or a technique of preventing corrosion of an Al wiring formed over the CVD-TiN film as an upper electrode of a capacitor insulating film.